The production of bis(hydroxyalkyl) esters of benzenedicarboxylic acids such as bis(2-hydroxyethyl) terephthalate has become of significant commercial importance in recent years because these diesters can be polymerized to form linear super polyesters. These polyesters such as polyethylene terephthalate are widely used in textiles, tire cord, and the like.
The present invention has developed from the investigation of new polymeric compositions derived from bis(2-hydroxyethyl) terephthalate which is now an inexpensive and readily available commercial product. It was deemed desirable to endeavor to introduce the excellent properties of bis(2-hydroxyethyl) terephthalate into polymeric compositions which would have unique properties and versatility in applications commonly served by polyester type thermoplastic resins.
Thus, it is an object of the present invention to provide novel polymers based on bis(2-hydroxyethyl) terephthalate.
It is another object of the present invention to provide polyester polymers which contain phosphorus.
It is still another object of the present invention to provide thermoplastic phosphonate polymers which are valuable as plasticizers for imparting flame retardancy to polyester plastics, or as additives for modifying the properties of resin compositions.